espocrm-base/application/Espo/Resources/metadata/entityDefs/NextNumber.json

{
    "fields": {
        "entityType": {
            "type": "varchar",
            "index": true,
            "maxLength": 100
        },
        "fieldName": {
            "type": "varchar",
            "maxLength": 100
        },
        "value": {
            "type": "int",
            "default": 1
        }
    },
    "indexes": {
        "entityTypeFieldName": {
            "columns": ["entityType", "fieldName"]
        }
    }
}